All known tritium measurements made of Hawaii rainwater, ocean water, surface water, and ground water are summarized. Ocean water yielded 10 to 20 T.U. in 1963-65. Tritium in rainwater rose from a
low 6 T.U. in 1961 to a 1963 summer peak of 373 T.U., exhibited strong seasonal fluctuations, and declined to 43 T.U. in mid-1965. Groundwater samples collected in late 1966 on Oahu ranged between 24 to 0.5 T.U. Ground-water samples with high tritium count were taken from high-level water; those with considerably less tritium were basal water and the one with the least tritium was basal water farthest down gradient and below a 1100-foot caprock in Ewa Beach, Oahu. The facilities of the Tritium Laboratory at the University of
Hawaii are described. The present basic unit for tritium analysis utilizes liquid scintillation with electrolysis for environment of low-level samples.